<template>
	<view class="content" :style="{'height': `${scrollH}px`}">
		<view class="cont">
			<scroll-view scroll-y scroll-with-animation class="cont_view menu-scroll-view" :scroll-top="scrollTop"
				:scroll-into-view="itemId" :style="[menu_left]">
				<view v-for="(item,index) in tabbar" :key="index" class="menu_item"
					:style="[menu_left_active,current == index?menu_left_activea:{}]" @tap.stop="swichMenu(index)">
					<view class="menu_item_name">{{item[keyName]}}</view>
					<view class="y_deg pa" v-if="current == index"></view>
				</view>
			</scroll-view>
			<scroll-view :scroll-top="scrollRightTop" scroll-y scroll-with-animation :style="[menu_right]"
				@scroll="rightScroll">
				<view class="menu_right_view">
					<view class="menu_right_item" :id="'item' + index" v-for="(item , index) in tabbar" :key="index">
						<view class="menu_right_title">{{item[keyName]}}</view>
						<view class="">
							<slot name="scrollArr" :scroll_list='item.list'></slot>
						</view>
					</view>
				</view>
			</scroll-view>
		</view>
	</view>
</template>
<script>
	/*
	 * zhSlidingMenu 分类商品-单向联动 + 双向联动，支持自定义商品内容
	 * @property {Number} tabbar 分类数据
	 * @property {Number} keyName 从tabbar元素对象中读取的键名
	 * @property {Number} scrollH scroll高度
	 * @property {Object} menu_left 左侧样式
	 * @property {Object} menu_left_active 左侧未选中样式
	 * @property {Object} menu_left_activea 左侧选中样式
	 * @property {Object} menu_right 右侧样式
	 */
	export default {
		props: {
			tabbar: {
				default: () => []
			},
			keyName: {
				default: () => 'name'
			},
			scrollH: { //滑动高度
				default: () => 667
			},
			menu_left: { //
				typeof: Object,
				default: () => ({
					'width': '200rpx',
					'background': '#F8F8F8',
				})
			},
			menu_left_active: {
				typeof: Object,
				default: () => ({
					'color': 'rgba(35,35,35,0.7)',
					'font-weight': '400',
					'font-size': '26rpx',
				})
			},
			menu_left_activea: {
				typeof: Object,
				default: () => ({
					'color': '#0BC5AE',
					'font-weight': '500',
					'background': '#fff',
				})
			},
			menu_right: { //右侧样式
				typeof: Object,
				default: () => ({
					background: '#fff',
				})
			}
		},
		data() {
			return {
				scrollTop: 0, //tab标题的滚动条位置
				oldScrollTop: 0,
				current: 0, // 预设当前项的值
				menuHeight: 0, // 左边菜单的高度
				menuItemHeight: 0, // 左边菜单item的高度
				itemId: '', // 栏目右边scroll-view用于滚动的id
				arr: [], //左侧菜单距离登录距离列表
				scrollRightTop: 0, // 右边栏目scroll-view的滚动条高度
				timer: null, // 定时器

			}
		},
		mounted() {
			this.getMenuItemTop()
		},
		methods: {
			// 点击左边的栏目切换
			async swichMenu(index) {
				if (this.arr.length == 0) {
					await this.getMenuItemTop();
				}
				if (index == this.current) return;
				this.scrollRightTop = this.oldScrollTop;
				this.$nextTick(() => {
					this.scrollRightTop = this.arr[index];
					this.current = index;
					this.leftMenuStatus(index);
				})
			},
			// 获取一个目标元素的高度
			getElRect(elClass, dataVal) {
				new Promise((resolve, reject) => {
					const query = uni.createSelectorQuery().in(this);
					query.select('.' + elClass).fields({
						size: true
					}, res => {
						// 如果节点尚未生成，res值为null，循环调用执行
						if (!res) {
							setTimeout(() => {
								this.getElRect(elClass);
							}, 10);
							return;
						}
						this[dataVal] = res.height;
						resolve();
					}).exec();
				})
			},
			// 观测元素相交状态
			async observer() {
				this.tabbar.map((val, index) => {
					let observer = uni.createIntersectionObserver(this);
					// 检测右边scroll-view的id为itemxx的元素与right-box的相交状态
					// 如果跟.right-box底部相交，就动态设置左边栏目的活动状态
					observer.relativeTo('.right-box', {
						top: 0
					}).observe('#item' + index, res => {
						if (res.intersectionRatio > 0) {
							let id = res.id.substring(4);
							this.leftMenuStatus(id);
						}
					})
				})
			},
			// 设置左边菜单的滚动状态
			async leftMenuStatus(index) {
				this.current = index;
				// 如果为0，意味着尚未初始化
				if (this.menuHeight == 0 || this.menuItemHeight == 0) {
					await this.getElRect('menu-scroll-view', 'menuHeight');
					await this.getElRect('menu_item', 'menuItemHeight');
				}
				// 将菜单活动item垂直居中
				this.scrollTop = index * this.menuItemHeight + this.menuItemHeight / 2 - this.menuHeight / 2;
			},
			// 获取右边菜单每个item到顶部的距离
			getMenuItemTop() {
				new Promise(resolve => {
					let selectorQuery = uni.createSelectorQuery().in(this);
					selectorQuery.selectAll('.menu_right_item').boundingClientRect((rects) => {
						// 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
						if (!rects.length) {
							setTimeout(() => {
								this.getMenuItemTop();
							}, 10);
							return;
						}
						rects.forEach((rect) => {
							// 这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
							this.arr.push(rect.top - rects[0].top);
							resolve();
						})
					}).exec()
				})
			},
			// 右边菜单滚动
			async rightScroll(e) {
				this.oldScrollTop = e.detail.scrollTop;
				if (this.arr.length == 0) {
					await this.getMenuItemTop();
				}
				if (this.timer) return;
				if (!this.menuHeight) {
					await this.getElRect('menu-scroll-view', 'menuHeight');
				}
				setTimeout(() => { // 节流
					this.timer = null;
					// scrollHeight为右边菜单垂直中点位置
					let scrollHeight = e.detail.scrollTop;
					for (let i = 0; i < this.arr.length; i++) {
						let height1 = this.arr[i];
						let height2 = this.arr[i + 1];
						// 如果不存在height2，意味着数据循环已经到了最后一个，设置左边菜单为最后一项即可
						if (!height2 || scrollHeight >= height1 && scrollHeight < height2) {
							this.leftMenuStatus(i);
							return;
						}
					}
				}, 10)
			}
		}
	}
</script>

<style lang="scss" scoped>
	.content {
		display: flex;
		flex-direction: column;

		.cont {
			flex: 1;
			display: flex;
			overflow: hidden;

			.cont_view {
				height: 100%;

				.menu_item {
					position: relative;
					padding: 24rpx 12rpx;

					.menu_item_name {
						display: -webkit-box;
						-webkit-box-orient: vertical;
						-webkit-line-clamp: 1;
						overflow: hidden;
						text-align: center;
					}

					.y_deg {
						width: 6upx;
						height: 40upx;
						background: #0BC5AE;
						border-radius: 3upx;
						position: absolute;
						left: 0%;
						top: 50%;
						z-index: 99;
						transform: translate(0, -50%);
					}
				}
			}
		}
	}

	.menu_right_view {
		padding: 24upx;

		.menu_right_item {
			margin-bottom: 30rpx;
		}

		.menu_right_item:last-child {
			min-height: 100vh;
		}
	}

	.menu_right_title {
		color: #232323;
		font-weight: bold;
		font-size: 32rpx;
		display: -webkit-box;
		-webkit-box-orient: vertical;
		-webkit-line-clamp: 1;
		overflow: hidden;
	}
</style>